blob: 0c6a4209743afe02849f32f3ca51c2a0948c90ae [file] [log] [blame]
// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
/// The class `UriResolver` implements the rules for resolving "dart:" and
/// "package:" URIs.
class UriResolver {
/// The URI scheme used for "package" URIs.
static const PACKAGE_SCHEME = 'package';
/// The URI scheme used for "dart" URIs.
static const DART_SCHEME = 'dart';
/// A map from package name to the file URI of the "lib" directory of the
/// corresponding package. This is equivalent to the format returned by
/// the "package_config" package's parse() function.
final Map<String, Uri> packages;
/// A map from SDK library name (e.g. `core` for `dart:core`) to the file URI
/// of the defining compilation unit of the SDK library.
final Map<String, Uri> sdkLibraries;
UriResolver(this.packages, this.sdkLibraries);
/// Converts "package:" and "dart:" URIs to the locations of the corresponding
/// files.
/// If the given URI is a "package:" or "dart:" URI, is well formed, and names
/// a package or dart library that is recognized, returns the URI it resolves
/// to. If the given URI is a "package:" or "dart:" URI, and is ill-formed
/// or names a package or dart library that is not recognized, returns `null`.
/// If the given URI has any scheme other than "package:" or "dart:", it is
/// returned unchanged.
/// It is not necessary for the URI to be absolute (relative URIs will be
/// passed through unchanged).
/// Note that no I/O is performed; the URI that is returned will be
/// independent of whether or not any particular file exists on the file
/// system.
Uri resolve(Uri uri) {
if (uri.scheme == DART_SCHEME || uri.scheme == PACKAGE_SCHEME) {
var path = uri.path;
var slashIndex = path.indexOf('/');
String prefix;
String rest;
if (slashIndex >= 0) {
prefix = path.substring(0, slashIndex);
rest = path.substring(slashIndex + 1);
} else {
prefix = path;
rest = '';
Uri libUri;
if (uri.scheme == PACKAGE_SCHEME) {
if (slashIndex < 0) return null;
libUri = packages[prefix];
} else if (uri.scheme == DART_SCHEME) {
libUri = sdkLibraries[prefix];
if (libUri == null) return null;
return libUri.resolve(rest);
} else {
return uri;